Alongside the development of petrochemical industry, the application of synthetic polymers is becoming increasingly widespread, particularly a great quantity of synthetic polymeric substances are used as packing materials. At the same time, scraps of these materials are accumulated, among which the foam polystyrene occupies a significant proportion. The foam packing material causes a serious environmental pollution owing to the low density and the bulky volume. The other kind of scraps from polystyrene is also difficult to be processed and recycled. Burning and burying of the polystyrene scraps not only cause the resource waste, but also are not able to settle the pollution. In recent years a lot of research work has been carried out for recycling the discarded polymers. Attempts to obtain useful starting materials by means of pyrolysis and decomposition have been undertaken in many countries.
Yamamoto Makoto et al of Technology Institute, Waseda University in Japan, adopted distillation reactors to pyrolyze polystyrene (average molecular weight 99,000) at the temperature of 270.degree. C., obtaining a liquid pyrolysis product containing 20% of styrene. JP74129772 disclosed a process of pyrolyzing polystyrene, which, using a pyrolysis tube 3 mm in diameter, involves pyrolysis of 16.6% solution of polystyrene in methylnaphthalene or tetralin at the temperature of 300.degree. C. with the pyrolysis time of 506 sec. The recovery rate of styrene is 65.5%, and the solvent (s) could be repeatedly used. JP49099326 revealed a continuous method of preparing styrene through the pyrolysis of polystyrene. This method involves the introduction of overheated steam into a pyrolysis reactor containing a solution of polystyrene in benzene in the presence of copper powder as a catalyst at the temperature of 300.degree. C. The recovery rate of styrene is 58.3%. The disadvantage of the methods described above consists in a requirement of a large quantity of aromatic compounds as solvent (s) for dissolution of polystyrene, which are costly and hard to be realized on an industrial scale. Another disadvantage of the methods described above is the low recovery rate of styrene monomer.